I had a 2002 CTD and did all the maintenace after I got it from the PO including the VP44 replacement. You can get the codes from the computer without a code reader. Check the Cummins turbo web sites for how to do it and a list of the codes. Basically it involves turning the ignition key to the on position, then off, them on again a few times w/o starting. Codes are displayed in the odometer window. You can't clear them only display them. Good luck, I wish I still had that truck.